ALTERATION OF PLATELET-ASSOCIATED MEMBRANE-GLYCOPROTEINS DURING EXTRACORPOREAL APHERESIS OF PERIPHERAL-BLOOD PROGENITOR CELLS

In extracorporeal circulation, blood is affected by artificial biomate rials and shear forces. We investigated the effects of peripheral bloo d progenitor cell (PBPC) apheresis on the kinetics and level of platel et membrane antigen expression in 11 breast cancer and 13 testicular c ancer patients, After mobilization with rhG-CSF, continuous-flow apher esis was performed, Expression of structural antigens CD41a and CD42b and activation-dependent antigens CD62p, CD63, and fibrinogen was anal yzed by flow cytometry at fixed time intervals, Initial changes occurr ed in all of the antigens within minutes, followed by a progressive in crease in the mean channel fluorescence intensities (MCFI) of CD62p fr om 26 +/- 8 (mean +/- SD) to 73 +/- 29 (p < 0.05), CD63 from 22 +/- 5 to 51 +/- 16 (p < 0.05), and antifibrinogen from 120 +/- 20 to 356 +/- 154 (p < 0.05), In contrast, CD4la and CD42b fluorescence decreased d uring apheresis (p < 0.05 for both), The more rapid sequestration of P -selectin-expressing platelets known to occur during extracorporeal PB PC apheresis suggests that platelet activation may be associated with the loss of platelets during this procedure, In addition, alteration o f platelet surface antigens increases thrombogenic potential and may r educe the in vivo efficacy of the platelet hemostatic potential.